Search Documents

By J. A. Herbst, K. Rajamani, M. Siddique

This paper presents an investigation of the accuracy of population balance model predictions for ball mill scale-up. Experiments performed in 25.4 x 29.2 cm (10 x 11.5) batch mill are used to estimate linear grinding rate parameters that, in turn are scaled according to specific power draft to predict performance in 381 x 292 mm (15 x 11.5 in.) and 762 x 457 mm (30 x 18 in.) batch and continuous ball mills, respectively. Results are presented for wet and dry grinding of two homogeneous solids, limestone (soft) and quartz (hard), and one heterogeneous solid, a complex molybdenite ore. In all cases good agreement between predicted and experimental product size distributions was obtained.

Jan 1, 1983

By José G. Aguilera

With the imperfect knowledge that me have of the geology .of the country in general, and of the numerous mining districts in particular, it is impossible to present an accurate idea of the geographical and geological distribution of the mineral deposits of the Mexican Republic. But, notwithstanding this, it is elear that the deposits are concentrated in limited regions of the country, and that certain deposits are so closely associated as to indicate, beyond doubt, a genetic relationship. The mineral deposits are numerous, and the most of them are found in the western part of the country in a zone following a SE.-NW. direction from Oaxaca to Sonora. In the eastern

Jan 1, 1902

By A. M. Abouzeid, S. Chander, D. W. Fuerstenau

Today numerous ores contain valuable minerals in finely disseminated form; and although the recovery of these fine mineral particles is generally exceedingly difficult, diminishing raw material resources necessitates the recovery of such mineral values. In many systems, the efficiency of recovering fine particles is still extremely low and often fine particles must be discarded as slimes. However, in recent years, various advances have taken place in the recovery of mineral particles in the very fine size range. In this paper, the background and performance of a number of processes for fine particle processing and separation are reviewed and discussed, particularly from the point of view of how fine particle recovery might be improved.

Jan 1, 1979

By L. J. Parkinson

IN striking contrast to American mining engineering schools, in Europe a new president, known as the Rektor Magnificus, is elected each year or alternate year. An exception is Italy, where election is for a period of three years. The Rektor, who is elected by the full professors, must also be a professor and full-time member of the faculty. In most cases there is a Senate, composed of 5 to 14 full professors, some elected and some appointed, which controls the Rektor in policy decisions, but in some institutions there is no such controlling body. In the same way deans for each faculty or college are selected at the same intervals from among the full professors concerned.

Jan 1, 1958

By Donald E. Crowell

Due to falling metal prices and depletion of ore reserves, lead- zinc mining in the Leadville, Colo., area gradually came to a halt in the 1950's. Exploration work continued, however, and by 1969 sufficient ore had been blocked out to warrant sinking a shaft and erecting a new concentrator to treat 700 tpd. The new shaft and concentrator were to be located in Iowa Gulch several miles east of Leadville at an elevation of 11,100 ft. The Leadville project is a joint venture between Newmont Mining Co. and Asarco, with Asarco being the operator. Design work began in the fall of 1969. Engineering was done by Torkelson Engineering Co. of Salt Lake City in conjunction with the central engineering department of Asarco. The plant was constructed by Stearns-Roger Corp. Construction began in the spring of 1970 and the plant went onstream in April 1971.

Jan 11, 1972

PRESIDENT Truman's economic report to Congress calls for an increase of 40 billion dollars in the value of goods and services produced in the United States by 1955; this is an increase of 16 percent over our 1949 production. If such an increase is to be realized, it will be possible only by a comparable increase in the production of steel-the keystone of our economy. Going one step further, since the raw materials of steel are iron ore, limestone, and coal, the President's goal can be reached only through the efforts of the mining industry. Coal and limestone reserves are not critical at this time, but the abundance of iron ore reserves has been subject to controversy. In this issue we proudly present "Cerro Bolivar--Saga of a Crisis in Iron Ore Averted" (a story which has been seven years in the making and three years in the getting).

Jan 2, 1950

One of our members, in Colombia, has written the following interesting account of his experience in trying to remit his dues to the Institute. "Last year I was away at the end of the year and on my return I was unable to obtain a draft in Honda until April, I believe. To avoid delay this year I remitted cash, early in January, to a friend in Bogota who I imagined could sell or procure for me various small drafts to cover my annual subscriptions. After many weeks' delay, I was informed that he could not get them for me and was remitting the cash to Honda where they were obtainable. After another long delay, I was informed that no one in Honda would sell drafts or checks for small amounts. Eventually I found a friend who was willing to oblige me in the matter and at once forwarded the amount."

Jan 8, 1919

INTERNATIONAL ENGINEERING CONGRESS This Congress will be held under the auspices of five National Engineering Societies, of whi h the Institute is one. The sessions will be held in 11 sections and the proceedings will be published in 10 volumes of 500 pages each, of which Volume 8 will contain the papers and proceedings on Mining Engineering and Metallurgy. The membership fee of $5 will entitle the holder to the volume of General Proceedings and Index, and, in addition thereto, any other single volume chosen. Other volumes may be subscribed for according to a sliding scale depending upon the number of volumes taken. The Institute will have a meeting in San Francisco during 1915, and it is desirable for our members to join the International Engineering Congress at in early date in order that their support of the enterprise may be given in its early stages, when it is most needed.

Jan 2, 1914

By C. W. Parisi

Use of high-expansion foam for controlling mine fires was first made known in a published announcement in June, 1956, by representatives of the Safety in Mines Research Establishment, Buxton, England. In 1957, the United States Bureau of Mines, interested in this new method of controlling mine fires which could not be approached or extinguished by conventional methods, began to investigate the practicability of the foam-plug technique under American mining conditions at its experimental coal mine in Bruceton, Pa. Results of these experiments proved the potentialities of controlling mine fires with foam. The USBM conducted numerous demonstrations at its experimental mine to show this foam-plug method to groups of coal mining men, many of which were impressed by the action of the foam as it moved away from the netting toward an open fire and its ability to control the fire in a very short time.

Jan 2, 1961

By B. P. Bellport

When tunneling crews set world records in rates of advance by boring up to 403 ft in a single day and 6851 ft in a month, then the age of rapid under- ground excavation is near at hand with its attendant economies. Boring machines excavate tunnels with uniform diameters and smooth walls and only about 5% overbreak compared to 20% overbreak experienced by conventional drill-blast methods. This advantage minimizes the concrete required for lining and because a circular section is more nearly self-supporting there is less of a need for supports before the concrete is placed. In addition, laser beam guidance improves the accuracy of excavation with boring machines. In the first successful application of laser guidance for boring machines in the Navajo Indian Irrigation Project, the final excavation was within 5/8 in. of the established line and grade over a 10.079- ft advance.

Jan 1, 1971

By John M. Pitt

Shear strength assessment and the associated variability in rock masses historically have been hindered by high costs and biases in laboratory testing programs. An in situ direct shear device was developed on the principle of the previous borehole shear device for soils. Using wedge action to simultaneously apply normal and shear stress to an envelope of material on the periphery of a borehole, the device develops a complete Mohr-Coulomb failure envelope. Tests performed in homogeneous materials show expected strengths and their variability equivalent to laboratory tests. However, tests in a structurally non- homogeneous coal did not display significant variability. A 38 mm diam borehole was used in this work; however, larger or smaller bore- holes may also be used within the size limits of the device. The device is employed in holes commonly drilled for rock bolt placement, at 1 to 2 minutes per test.

Jan 1, 1984

By L. A. Roe

The flotation of fine particles less than five microns in diameter and the flotation of liquids from liquids generally requires bubble generation methods different than methods used in dispersed air type machines used in mineral flotation. Conditions in the separatory zone in mineral cells are generally more dynamic as compared to the quiescent conditions often absolutely necessary for the flotation of fine particles and liquids. An example of quiescent flotation with very fine bubbles is the lithium flotation plant which operated at Trona, California for 34 years, until it ceased operations in 1978. A review of the process development and the commercial flotation operations at Trona is given in this paper. The clarification of oil field brines by flotation of the oil from the brine has been used for over twenty-five years. Recent installations related to the Prudhoe Bay oil field and the Alaska pipeline are described.

Jan 1, 1980

By Betty J. Laswell, Gerald W. Laswell

If recent trends in the rotary drill market are indicative of future surface mining operating practice, then the move to scaled-up mining equipment by manufacturers may soon be over. Of the 48 different rotary drills currently produced by 12 manufacturers, over 60% were introduced within the past five years. By far, the new drills have been in the "small" class, capable of producing up to a 229-mm-diam (9-in.) blasthole with 222 kN (50,000 lb) or less of down pressure. New rotary drills in the "large" class, capable of producing a 311-mm-diam (12 1/4-in.) blasthole with up to 423 kN (95,000 lb) down pressure, have also been prominent. In the super-size category, new drills producing blasthole sizes to 444-mm-diam (17 1/2-in.) with up to 578 kN (130,000 lb) have been minimal.

Jan 7, 1978

By Stephen Taber

INTRODUCTION THE term asbestos, as commonly used, includes half a dozen minerals all having a well-developed fibrous structure, but differing in chemical composition and in some of their physical, properties. In its strict application the name is limited to the fibrous varieties of the monoclinic amphiboles. Commercially, however, the most important of the asbestiform minerals is chrysotile, a fibrous variety of serpentine. About 95 per cent. of the asbestos used in manufacturing is chrysotile, and it commands a much higher price than any of the other fibrous minerals now on the market. Although the production of asbestos has increased rapidly in recent years, comparatively little has been published concerning its origin. The present paper is preliminary in its nature, and therefore does not pretend to exhaust the subject. The ideas herein developed are the result of field investigation, laboratory experiments in the growth of fibrous

Jan 10, 1916

By James P. Kimball

In a paper which I had the honor to present to the Institute at the Montreal meeting, September 1879,I took occasion to refer incidentally to certain practical difficulties in the sampling of coal-seams {Trans. Vol. VIII., p. 181-3). This reference was particularly to the unequal distribution of sulphur in the form of pyrite, and to the necessity of discriminating between the several members or " benches " of a coal seam as to their relative proportion of visible sulphur. What is a practically truthful estimation of the sulphur of a coal seam, is not necessarily the estimation of an average of sulphur in any given line of cross-section of the seam. Cornparatively speaking, the range of sulphur in quantity is generally so low that errors in its determination, arising from neglectful sampling or from slips in the laboratory, fall chiefly upon this single ingredient. Not so,

Jan 1, 1884

By Douglas Ashmead

In his paper Mr. Braley makes no mention of the bacteriological aspects of the problem. It is now quite well established that certain bacteria play a major role in formation of acid mine waters, and it is a simple matter in the laboratory to show that under sterile conditions the rate of acid production from a pyrites suspension is only about one quarter of that obtained from a similar suspension inoculated with drainage from a mine producing an acidic pit water. Under sterile conditions the oxidation is due to direct chemical action and, from the evidence just given and from much other evidence, this increase under nonsterile conditions is due to certain bacteria. Experiments recently completed, and shortly to be published, have shown that this bacteriological oxidation can be prevented by the maintenance of pH conditions above 4. It was found that to raise this pH above 4 at the beginning of the experiments was not sufficient but that, due to the continuing chemical oxidation, alkali had to be added daily to maintain the pH conditions above 4. The amount of alkali added, however, over a fixed period, was only about one quarter of the alkaline equivalent of the acid produced when pH conditions were not controlled over an equal period. The opinion expressed by Mr. Braley that sodium hydroxide has little or no effect on the rate of oxidation of pyrites is not substantiated by the above experiments. The writer does not claim that these results show a practical solution to the problems, especially in abandoned workings, but feels that the application of an alkaline coating, such as lime wash, to exposed accessible workings might be well worth trying. S. A. Braley (author's reply)—In 1919 Powell and Parrl suggested that bacteria, or some catalytic agent, hastened the oxidation of pyritic or marcastic sulfur in coal. Carpenter and Herndon (1933)' attributed the action of Thiobacillus thiooxidans. Colmer and Hinkle (1947)3 observed an organism similar to T. thiooxidans and another organism that oxidized iron. Leathen and Braley 9rst discovered this organism in 1947 in a sample of water from the overflow of the Bradenville mine (Westmoreland County, Pennsylvania). They characterized the organism in 1954" and gave it the name Ferrobacillus ferrooxidans. Although Temple and Colmer (1951)' had suggested the name Thiobacillus ferrooxidans, since they claimed it oxidized both ferrous iron and thiosulfate, we have found that pure cultures of the organism do not oxidize thiosulfate, hence the name F. ferrooxidans. In 1955 Ashmead7 isolated an organism, similar to the one called Thiobacillus ferrooxidans by Temple and Hinkle, from acid mine water in Scotland. It is probable that this organism was F. ferrooxidans. In 1954 Bryner, Beck, Davis, and Wilsonh reported microorganisms in effluents from copper mine refuse. These organisms appeared to be similar but were not in pure culture. In view of this history of bacterial investigation of acid mine water and our own ten years of experience, we do not agree with Mr. Ashmead that bacteria play a major role in acid formation. We do not find that any of these bacteria will directly oxidize pyritic material. They do, however, augment the chemical formation of sulfuric acid by atmospheric oxidation. In two papers in 1953% eathen, Braley, and McIntyre discuss the role of bacteria in acid formation and postulate the mechanism through which they operate. Mr. Ashmead in his discussion of my paper has assumed that this work was carried on in the presence of acid mine water in which bacteria would be present. This was not the case. Strictly sterile conditions were not maintained, but the organisms present in mine drainages were definitely absent in these experiments. We believe that we have demonstrated that alkalis do not inhibit the chemical oxidation of pyritic material. This is also indicated by Mr. Ashmead's discussion in which he says that alkali must be added daily due to the continuing chemical oxidation. It is interesting to note that Mr. Ashmead finds that maintenance of pH above 4.00 decreases the activity of the bacteria. We have found also that a decrease in pH below 2.8 also inhibits its activity. Table XIII of published data'" illustrates the decrease in activity with increased acidity, although pH values are not given. These values are in comparison with uninoculated controls and show the marked increase in acidity up to 22 weeks but a decline at 29 weeks, at which time the experiment was terminated. It is probable that after a longer period only chemical oxidation would have continued. From our studiesv we have postulated that the iron oxidizing bacterium (Ferrobacillus ferrooxidans) oxidizes the ferrous iron, resulting from chemical oxidation, to ferric iron. The ferric iron then aids the atmospheric oxidation of the sulfuritic material and is itself reduced to ferrous iron, which in turn acts as food for the autotrophic bacteria. Study of the physiologic properties of F. ferrooxidans shows that its preferred pH is about 3.00 and its activity decreases with variation in either direction. It is extremely inactive above pH 4.00 and below 2.5. This inactivity above 4.00 is indicated by Mr. Ashmead's observations. These properties of F. ferrooxidans then correlate perfectly with our hypothesis. Ferrous iron is oxidized very slowly by atmospheric oxygen in highly acid sohtion and since the bacteria become inactive, acid is formed only by atmospheric oxidation. At a pH of 4.00 or above iron is more readily oxidized by atmospheric oxygen, but the bacterial activity is decreased. However, with a pH above 4.00 the ferric iron is removed from the field of activity since its soluble sulfate hy-drolyzes and precipitates the iron as ferric hydroxide or a basic sulfate. As we have shown in the paper under discussion, the alkali does not inhibit the chemical oxidation, and thus the acid formation continues. This

Jan 1, 1957

By Edward J. Felten

Binary Cr-A1 alloys containing from 2.5 to 30 wt pct Al and 0.7 wt pct Y were heated in oxygen, air, and nitrogen between 1000" and 1200°C. The reacLivity of the alloys was found to be dependent both on the alloy composition nnd the nature of t he atmosphere. In oxygen, nllojs containing up to 15 to 20 wt pct A1 reacted to produce an external scale of Crz03 and a subscale consisting Predominently of Al203. Alloys contazning 20 to 30 wt pct A1 react in oxygen to produce an A1203 external scale and little m no subscale. The latter alloys were markedly more oxidation resistant than those of low alurninum content. In air, the alloys on which an external Crz03 scale was formed were found to be permeable to nitrogen ns evidenced by the copious amomts of chromium and aluminum nilrides observed ns part of the subscale. The reactizities in nir (or nitrogen) of these alloys increase <m their aluminurn contents increase. However, alloys on which Al,O, us an external scale is formed were nol culnerable to nccelerated attack in air, and no eltldence of nitvide subscnles were observed. For all alloys, yttrium serwed pYimarily to improve oxide adhrence. THE role of chromium in the oxidation resistance of Fe-Cr alloys &apos;-&apos; and that of aluminum in Fe-Cr-A1 al10s&apos; has received considerable attention in recent years. This is understandable since many of these alloys have excellent oxidation resistance due to the formation of either a Cr203 or a-Ala03 film between the metal and the oxidizing atmosphere. Small additions of yttrium or other rare earth metals are effective in preventing spalling of the protective oxide from the metal substrate."" In contrast, little is known regarding the oxidation resistance of Cr-A1 alloys, although some work has been done by Tumarov et a1.&apos; The poor niechanical properties exhibited by Cr-A1 alloys make them undesirable for use as structural components, but their use as coatings cannot be disregarded. The use of chromium-rich aluminide coatings for refractory metal alloys is an example of the potential use of this type of sytem. The purpose of this work is to examine the oxidation behavior of Cr-A1 alloys containing 2.5 to 30 wt pct A1 and 0.7 wt pct Y. The effects of temperature, atmosphere, and thermal cycling have been determined. EXPERIMENTAL PROCEDURE The alloys used in this investigation can be divided into two groups. Those containing 2.5, 5, 7.5, and 10 wt pct A1 and 0.7 wt pct Y were extensively evaluated in the temperature range from 1000" to 1200°C. Alloys containing 15, 20, 25, and 30 wt pct A1 and 0.7 wt pct Y were tested only at 1200°C. All of the alloys were prepared by standard arc-melting techniques in the form of cylinders approximately 4 in. long and 19 in. in diam. Wafers were cut from the cylinders and subsequently subdivided into rectangular coupons. The alloys were brittle and therefore some cracks were found in almost all specimens. The coupons were prepared for oxidation by mechanically polishing through 600 grit Sic paper, and were thoroughly degreased just prior to testing. Two types of oxidation experiments were conducted, namely; cyclic tests in which the specimens were examined and weighed after each 2 hr exposure, and continuous thermal balance tests run in a controlled atmosphere (oxygen, air, or nitrogen) for 20 hr. In the former test the spalled oxide was not included when the specimens were weighed. The physical condition of a specimen was noted visually after each cycle and testing was continued either to failure or until the performance of the specimen was well characterized. Both Micro and Semi-Micro Thermal Balances (Ains-worth) were used in the continuous tests. The oxidized specimens were sectioned and prepared for metal log raphic examination. The specimens were polished through 600 grit Sic paper. After polishing through 6 and l p diamond, a final mechanical polish with Linde B-Alz03 was used. Specimens containing 2.5 pct A1 were etched electrolytically using a 10 pct oxalic acid solution at 4 v for about 2 sec. Selected specimens were examined in the electron microprobe analyzer. Oxide specimens were examined by standard X-ray diffraction techniques. EXPERIMENTAL RESULTS For convenience, the test results have been broken down according to the exposure temperature, and further subdivided according to the type of test and atmosphere employed. Because of the poor quality of the specimens a larger than normal amount of scatter was observed in the measured rate constants. Also, the evaluation of the weight gain data was done on a somewhat arbitrary basis and may not be truly representative. However, the results obtained do show a significant trend in behavior regarding both alloy composition and the nature of the oxidizing atmosphere. I) Oxidation Behavior at 1000°C. A) Continuous Oxidation estsin Oxygen. This series of experiments was run in the Ainsworth Micro-Thermal Balance using pure oxygen at a pressure of 76 mm Hg. Under these conditions all specimens oxidized in accordance with the parabolic rate law over a major portion of the exposure time; the rate constants appear in Table I. The oxide formed externally on all specimens was predominantly Cr,O,, which was generally adherent. In some cases a slight amount of spalling in the form of a fine powder was noted. a-A1203 was observed as a subscale, along with Yz03 in all alloys. Alloys containing up to 7.5 wt pct A1 oxidize more rapidly than the Cr-0.7Y alloy.

Jan 1, 1970

By Lo-Ching Chang, J. Chipman

The perennial and increasing interest in the chemical behavior of steelmaking slags has led to numerous attempts to formulate the thermodynamic properties of these solutions. The classical view is that of a solution of the component oxides in which certain acidic oxides are more or less completely held in combination with basic or metallic oxides, the nature of the interoxide compounds being derivable from the chemical behavior of the slag or from the mineralogy of a solidified specimen. The known electrical conductivity of slags has pointed to the existence of ions in the solution and a number of attempts have been made to account for the observed facts of slag behavior on the basis of a theory of complete ionization of the solution. It is the purpose of this paper to examine, in the light of ionic theory, a number of recently published series of data on slag-metal and slag-gas equilibria, with the purpose of obtaining a more complete or more satisfactory generalization than has been possible on either of the single bases of simple compound formation or complete ionization. The attempt to formulate the ionic constitution of a complex solution is fraught with many uncertainties. An ion is not something that can be plucked from the solution and examined in detail, nor can its true formula be determined with certainty by any single experimental method. In attempting to express the composition of a slag by various ionic formulas it can be expected that alternative hypotheses of essentially equal merit will present themselves. In the present state of early development of the ionic theory of slags, it may be necessary to make some rather arbitrary choices of ionic formulas in the absence of su- cient information to yield complete certainty. Acids and Bases The classification of slag-forming oxides as acidic or basic apparently dates back into the days of Berzelius. It is difficult to see how the concept could have originated in the early twentieth century when it was fashionable to define an acid or a base as an aqueous solution containing hydrogen or hy-droxyl ions. It is, however, entirely consistent with the modern and more general theory of acids and bases. In this theory, as originally formulated by G. N. Lewis,&apos; a basic molecule is one that has an electron pair which may enter the valence shell of another atom thus binding the two together by the electron-pair bond. An acid molecule is one which is capable of receiving such an electron pair into the shell of one of its atoms. The acid, the base, and the product of neutralization may be either ions or neutral molecules. The product of such a reaction may itself be a base or an acid if it is further capable of giving or accepting an electron pair. Thus a base is a donor of electrons, an acid, an acceptor. In oxide slags the typical and ever-present base is oxide ion, 0-—. In behavior and in importance it is analogous to hydroxyl ion, OH-, which is the typical base of aqueous solutions. There is nothing in the chemistry of slags which is quite analogous to the acid H30+ in aqueous solutions. This is not surprising for in slag systems there is nothing which can be designated as a solvent and no ubiquitous positive ion. The chemistry of slags is in fact more complex than the chemistry of aqueous solutions and the concepts which must be evoked in its study are correspondingly broader. In seeking a basis for a classification of slag-forming oxides as basic or acidic it must be remembered that these terms are not absolute but relative. A substance which acts as a base toward a second substance may act as an acid toward a third. This is less likely to happen among strong bases or acids than among the weak ones; there are numerous examples of weak acids which under the influence of a stronger acid behave as weak bases. Such substances are called amphoteric. A classification of the glass-forming oxides has been proposed by Sun and Silverman² and further developed by Sun3 in which the oxides are arranged in order of decreasing acidity or increasing basicity, each substance being potentially capable of acting as an acid toward substances below it in the list and as a base toward those above it. It is based upon the relative strengths of the metal-to-oxygen bond as determined by the energy required to dissociate the oxide into its component atoms.&apos; Data are available for computation of this energy, at least approximately, for the oxides of slags and glasses. In general those oxides from which it is most difficult to remove the positive atom are the strong acids while those in which it is most loosely held are the strong bases. It is in the latter, of course, that formation of oxide ion occurs most readily as, for example, in CaO which in solution ionizes to form the weak acid Ca++ and the strong base O—. The order of arrangement found by Sun is shown in the first column of Table 1, to which have been added the data for

Jan 1, 1950

By J. H. Swisher

The rate of internal sulfidation of austenitic Fe-Ti alloys in H2S-H2 gas mixtures is controlled primarily by sulfur diffusion, with counterdiffusion of titanium playing a minor role. At temperatures below 1100°C, enhanced diffusion along grain boundaries becomes important. The rate of internal sulfidation at 1300°C is approximately equal to the rate computed from the sulfur diffusion coefficient. The diffusion coefficient of titanium in y iron has been determined from electron microprobe traces in the base alloy near the subscale interface. The solubility of sulfur in Fe-Ti alloys has been measured in the temperature range from 1150° to 1300°C. The equilibrium sulfur content is found to increase with titanium content, due to the large effect of titanium on the activity coefficient of sulfur. The Ti-S interaction becomes stronger as the temperature decreases. TITANIUM as an alloying element in stainless steels is an effective scavenger for interstitial impurities, carbon in particular. Titanium is known to form stable sulfides; however extensive thermodynamic data on the Ti-S system are not available. Schindlerova and Buzek1 have shown that the Ti-S interaction in liquid iron is moderately strong. There have been no previous studies of the Ti-S interaction in solid iron. Internal sulfidation of Fe-Mn alloys was the subject of a recent investigation by Herrnstein.2 He found the rate of internal sulfidation to be an order of magnitude greater than predicted from available solubility and diffusivity data. A satisfactory explanation for the discrepancy could not be given. In the present study, the solubility of sulfur in austenitic Fe-Ti alloys was measured using a standard gas equilibration technique. Fe-Ti alloy specimens were also internally sulfidized. The rate of internal sulfidation was measured as a function of temperature and alloy composition. Supplementary electron micro-probe measurements were made to provide additional information on the nature of the internal sulfidation process. EXPERIMENTAL The starting materials were alloys containing 0.12, 0.24, 0.38, and 0.54 wt pct Ti. The alloys were made in an induction furnace by adding titanium to electrolytic iron that previously had been vacuum-carbon-deoxidized. The major impurity in the alloys as determined by chemical analysis was carbon. The carbon content of the alloys averaged about 100 ppm; metallic impurities were presented in concentrations of 50 ppm or less. Specimens were made in the form of flat plates, 0.03 by 2 by 4 cm for the equilibrium measurements and 0.5 by 1.5 by 3 cm for the rate measurements. The experiments were performed in a vertical resistance furnace wound with molybdenum wire and containing a recrystallized alumina reaction tube. In the gas train, flow rates of the reacting gases were measured using capillary flow meters. The source of H2S was a mixture of approximately 2 pct H2S in H2, which was obtained in cylinders from the Matheson Co. A chemical analysis was provided with each cylinder. The H2-H2S mixture was diluted with additional hydrogen to obtain the desired ratio of H2S to H2, and the resulting mixture was diluted with 30 pct Ar to minimize thermal segregation of H2S in the furnace. Argon was purified by passage over copper chips at 350°C and subsequently over anhydrone. Hydrogen was purified by passage over platinized asbestos at 450°C and then over anhydrone. The H2-H2S mixture was purified by passage over platinized asbestos and then over Pas. The samples used in the solubility measurements were analyzed for sulfur by combustion and iodometric titration. The subscale thickness in the internally sulfidized samples was measured on a polished cross section, using a microscope with a micrometer stage. Electron microprobe traces for titanium in solution were made on several samples that had been internally sulfidized. A Cambridge microanalyzer was used, and the known titanium content at the center of the specimen was used as a calibration standard. The procedure for the microprobe measurements will be described further when the results are presented. RESULTS AND DISCUSSION Equilibrium Data. Fig. 1 shows the sulfur concentration as a function of gas composition for three alloys equilibrated at 1300°C. The dashed line is based on data published by Turkdogan, Ignatowicz, and pearson3 for pure iron. The breaks in the curves are the saturation points for the alloys. The fact that the initial slope decreases with increasing titanium content indicates that titanium interacts strongly with sulfur in solution. To obtain information on the composition of the precipitating sulfide phase, the measurements described in Fig. 1 were extended to higher sulfur partial pressures. These results are shown in Fig. 2. (The initial portions of the curves are reproduced from Fig. 1.) The highest PH2s /pH2 ratio used is believed to be below the ratio required for the formation of a liquid sulfide phase. Time series experiments were used to study the approach to equilibrium in the samples. It was found that equilibrium with the gas phase was reached in less than 4 hr at 1300°C.

Jan 1, 1969

By M. R. J. Wyllie

The relationship between the electromotive force (E.M.F.) across a shale barrier and the concentrations of sodium chloride solutions on either side has been investigated. It is shown that the action of a shale barrier is analogous to a glass membrane separating two acid solutions of different hydrogen ion concentrations. The shale behaves as a sodium electrode and is responsive to the activities of the sodium ions in the two solutions in such a way that the potential can be calculated by means of the Nernst equation. This conclusion is confirmed by laboratory experiments. In a borehole the total E.M.F. of a shale cell is the algebraic sum of the ~otential across the shale and a boundary potential. The relationship between total E.M.F. and the resistivity ratio of two sodium chloride solutions is indicated for a number of formation temperatures. The E.M.F. thus predicted is then compared with the .elf potential read from an electric log and good agreement is demonstrated. Based on both the self potential and resistivity curves of the electrical log. a method is given for calculating connate water content in a bed having in-tergranular porosity and containing both connate water and hydrocarbons. INTRODUCTION The first paper on electrical well logging by C. and M. Schlumberger and E. G. Leonardon in 1934&apos; attributed the self potential curve principally to streaming potentials, i.e. to electroki-netic effects. Almost immediately great difficulties were encountered in reconciling many of the curves they obtained with this interpretation. and a ~econd paper&apos; by the same authors soon appeared. In this second paper self potentials were attributed to the combined effects of streaming potentials and electrochemical potentials, the electrochemical potential being considered the result mainly of the interaction of fluids of differing salt concentrations, i.e. a boundary potential, and partly of potentials set up at the faces of impermeable materials. Some experiments involving a gray clay for the impermeable material were quated. The Schlumbergers and Leonardon deduced from the equation for a simple boundary ~otential that the electrochemical potential, as opposed to the electrokinetic potential, could be expressed in the form E=Klog- .......1 pe where K is a constant, pm the mud resistivity. p, the resistivity of the connate water in a porous bed. However, no general expression for the constant K was obtained. Although the literature between 1934 and 1943 contains a number of quotations of their results, the valuable work of the Schlumbergers and Leonardon was not extended so that the electrochemical potential has been generally attributed wholly to boundary potentials between the mud in the borehole and the connate waters in porous formations. Unfortunately, however, the fundamental premise of all these papers, that a boundary potential can give rise to current flow in a borehole, is thermodynamically untenable. As will be shown. the fact that the electrochemical potential can be fairly accurately express as E = K log pm/pc, a form in which a boundary potential may also be written, is partly fortuitous. The boundary potential is indeed an integral part of the expression for the electrochemical potential in a horehole, but in magnitude it represents only about 20% of the total potential. In 1943 an important step in the elucidation of electrochemical potentials was made by Mounce and Rust3 who showed that if a wall of shale separated two compartments which contained saline solutions of different concentrations, and if the two solutions were themselves brought into contact in the pores of a porous inert membrane (such as unglazed porcelain) a current flowed through the shale and saline solutions. The direction of positive current was from the shale into the more dilute solution. The paper of Mounce and Rust, while repeating some of the observations of the Schlumbergers and Leonardon, seems to be the first to show that the shale was the seat of a genuine electrochemical effect capable of causing current flow. In the same paper Mounce and Rust pointed out the similarity between the fundamental conditions of their experiment and the conditions which existed when a bed of shale in the ground was simultaneously in contact with a porous sand containing saline connate water and mud fluid of salinity different from that of the water in the sand. Since it is now generally recognized that the S.P. curve measures ohmic potential changes in the mud fluid in the well bore resulting from changes in current flow, it is apparent that currents having their origin in the electrochemical interaction of mud filtrate and connate waters with shale beds are a very important portion of the total S.P. The work of Mounce and Rusta and others appears to indicate that, in general, the electrochemical portion of a particular kick on a S.P. curve far exceeds any electrokinetic potentials resulting either from streaming potentials or Dorn effects. The Dorn effect, or sedimentation potential. arises when small particles are allowed to fall through certain fluids under the influence of gravity. a difference of potential being observe? between two electrodes placed at different levels in the stream of falling particles. The Dorn effect is unlikely to affect seriously the S.P. curve as now measured. A successful analysis of the electrochemical aspects of the S.P. log should

Jan 1, 1949